Cyanide ion, CN-, is important in metal plating industries as well as in leaching matals from...

Cyanide ion, CN^-, is important in metal plating industries as well as in leaching matals from ores because it keeps metals dissolved under conditions where they would otherwise form solids (precipitate) and settle out of solution. It is important to maintain pH>10.5 in these solutions to avoid forming toxic hydrogen cyanide gas. If a solution is prepared by dissolving 10^-2M NaCN in water, will the pH be in the region where the solution is safe? What is {HCN} in the solution? The pKa of HCN is 9.24.

Expert Solution

NaCN ( Salt of weak acid and strong base) will be hydrolyzed in the following way...

NaCN + H₂O = HCN + NaOH

For the solution pH =0.5[ pK_w + pK_a + logC]....... (where C= conc. of salt = 10^-2M)

and [HCN] = √(K_wC/K_a)

Thus we get, pH = 0.5(pK_w + pK_a + logC)

= 0.5( 14 + 9.24 + log10^-2 )

= 0.5 ( 14 + 9.24 -2 )

= 10.62 > 10.5

So, pH of the solution will be in the safe region.

Given, pK_a = 9.24 ; We get, K_a = 5.75 × 10^-10

According to the second equation, [HCN]

= √(K_wC/K_a)

= √ { (10^-14 × 10^-2 )/ 5.75 × 10^-10}

= 4.2 × 10^-4 M

queen_honey_blossom answered 4 hours ago

Cyanide ion, CN–, is important in metal plating industries because it can keepmetals dissolved under conditions...

Cyanide ion, CN–, is important in metal plating industries because it can keepmetals dissolved under conditions where they would otherwise form solids(precipitate) and settle out of solution. The details of how this occurs arepresented in Chapter 11. It is important to maintain pH>10.5 in these solutionsto minimize release of toxic hydrogen cyanide gas. If a solution is preparedby dissolving 10-2MNaCN in water, will the pH be in the region where thesolution is safe? What is the HCN concentration in the...

A gold-plating business produces a waste with cyanide (CN–), which is a poisonous material. The cyanide...

A gold-plating business produces a waste with cyanide (CN–), which is a poisonous material. The cyanide can be oxidized in a two step process as shown below. Reaction 1: Cyanide to Cyanate: NaCN + NaOCl → NaCNO + NaCl Reaction 2: Cyanate Destruction to Gases 2 NaCNO + 3 NaOCl + H2O → 3 NaCl + N2 + 2 NaHCO3 How much bleach (NaOCl) in kg/yr is needed to safety destroy cyanide at the gold plating business if the waste...

3. Silver ion reacts with excess CN- to form colorless complex ion, Ag(CN)2-, which has the...

3. Silver ion reacts with excess CN- to form colorless complex ion, Ag(CN)2-, which has the formation constant Kf = 3.0 x 1020. Calculate the concentration of Ag+ in a solution prepared by mixing equal volumes of 2.0 X 10-3 M AgNO3 and 0.20 M NaCN.

A metal plating company is considering three different methods for recovering byproduct heavy metals from a...

A metal plating company is considering three different methods for recovering byproduct heavy metals from a manufacturing site’s liquid waste. The investment costs and incomes associated with each method have been estimated. All methods have a 10-year life. The MARR is 12% per year. Using internal rate of return method, determine which method should be selected. Method A B C Initial cost ($) -15,000 -18,000 -25,000 Annual income ($) 4,000 5,000 6,000 Salvage value ($) 1000 2000 -500 Life, years ...

Like to a hydrogen-ion buffer, a metal-ion buffer tends to maintain a particular metal-ion concentration in...

Like to a hydrogen-ion buffer, a metal-ion buffer tends to maintain a particular metal-ion concentration in solution. By rough analogy between the equations, HA(aq) ⇌ H+(aq) + A−(aq) K = Ka and CaY2− ⇌ Ca2+ + "EDTA" K = K'f-1 determine the total mass of Na2EDTA·2H2O (FM 372.24) which must be dissolved, along with 2.15 g of Ca(NO3)2·2H2O (FM 200.13), in 500.0 mL of solution (acid-buffered at pH 9.24) to give a calcium-ion buffer with pCa2+ = 8.70? For the...

Silver plating processes use Ag(CN)2- as the source of Ag+ in solution. To make the solution:...

Silver plating processes use Ag(CN)2- as the source of Ag+ in solution. To make the solution: 4.0 L of 3.00 M NaCN and 50.0 L of 0.200 M AgNO3 are combined. (a) What is the concentration of free Ag+ ions in solution? (b) Why is AgCl not used in this process? NOTE: We have not yet introduced the equilibrium constant Kf. An answer is needed that gets around Kf or slowly introduces the concept. Thanks! (Jespersen 7th edition 21.98)

balance the following redox reaction in basic solution Ag(s)+CN-(aq)+ O2(g) -->Ag (CN)2- (aq) cyanide is not...

balance the following redox reaction in basic solution Ag(s)+CN-(aq)+ O2(g) -->Ag (CN)2- (aq) cyanide is not participating in the electrochemical reaction but does associate with the silver ion formed in a second association reaction. Balance the electrochemistry first and then add in the cyanide in by adding an associative reaction to the redox reaction.

A complex ion is a species in which a central metal ion is attached to a...

A complex ion is a species in which a central metal ion is attached to a group of surrounding ions or molecules by coordinate covalent bonds. The surrounding species are called ligands. Within a ligand, the atoms that are directly attached to the metal ion (or atom) are called donor atoms. Most ligands contain a single donor atom (monodentate), but some contain two donor atoms (bidentate), six donor atoms (hexadentate), or another combination of donor atoms. A complex ion that...

Give examples from the literature of metal complexes with coordination numbers (CN) of 2, 3, 4,...

Give examples from the literature of metal complexes with coordination numbers (CN) of 2, 3, 4, 5, 6, 7 and 8 (formula, structure). What is the highest Coordination Number found for a metal ion?

A solution is formed by adding 3.60 grams of solid barium cyanide, Ba(CN)₂, to 250.0 ml...

A solution is formed by adding 3.60 grams of solid barium cyanide, Ba(CN)₂, to 250.0 ml of 0.170M sodium cyanide, NaCN. Calculate the pH of the resulting solution. You may assume that the barium cyanide dissolve completely and that the change in volume is negligible with the addition of the solid.

Question